Presentation
Signs of raised intracranial pressure. A CT scan was performed (not available) showing obstructive hydrocephalus with a mass in the posterior cranial fossa. A VP shunt was inserted and an MRI was requested for characterization.
Patient Data
There are mainly two intra-axial ill-defined peripheral cerebellar masses measuring approximately (5 x 4.5 x 3.5 cm) on the right and (4.2 x 2 x 1.7 cm) on the left. They are of low signal on T1, iso-to high signal on FLAIR/T2 with moderate heterogeneous/nodular enhancement on postcontrast sequences, and restricted diffusion on DWI/ADC. The adjacent lateral/sigmoid sinuses are patent. Both masses show transtentorial extension (mainly on the right) well-visualized on the coronal postcontrast sequence. There is mild surrounding vasogenic edema with a mass effect on the 4th ventricle which is laminated and displaced to the left as well as a tonsillar herniation through the foramen magnum.
Case Discussion
The patient went on to have surgical resection of the tumor. The histopathological exam with an immunohistochemistry study confirms the diagnosis of a medulloblastoma - SHH subgroup (histological subtype: desmoplastic/nodular medulloblastoma with extensive nodularity -MBEN).
Medulloblastoma - sonic hedgehog (SHH) subgroup is most commonly seen in adults and infants. They are considered as the second most common medulloblastoma and most frequently located laterally within the cerebellar hemispheres.
Additional contributor: ZE. Boudiaf, MD, CHU Constantine, Algeria